1. Field of the Invention
The present invention relates to a production method of a metallic decorative sheet, and a production method of an insert molded body using the metallic decorative sheet.
2. Description of the Related Art
Conventionally, a molded body formed by coating a metallic decorative sheet (having a quality like metal) on a thermoplastic resin molded body has been known. The molded body is produced according to an insert molding by disposing preliminarily the metallic decorative sheet in a die and injecting thermoplastic resin into a cavity of the die for forming the thermoplastic resin molded body. The molded body is commonly used in a display portion, a touch panel or the like of home electric appliances.
The metallic decorative sheet is formed in such a way that a back surface thereof is printed with a design of words, graphics or the like in non-metallic ink, and the entire back surface except the design part is laminated by metal thin-film layers.
As a production method of the metallic decorative sheet, there has been known one, for example, as illustrated in FIG. 4, the production method comprises steps of: printing on one surface of a transparent thermoplastic resin film 111 a design 130 to be displayed on an outer surface of the molded body 100, vapor depositing thereon a metal thin-film layer 112, subsequently printing a non-specular ink layer 114 for preventing the metal thin-film layer 112 from being seen through, and finally printing a binder layer 115 for binding with a thermoplastic resin molded body 120 (for example, refer to Japanese Patent Laid-open No. 2005-288720).
There has also been known a method to compose the metal thin-film layer 112 of a specular ink layer through specular ink printing (for example, refer to Japanese Patent Laid-open No. 2009-6613).
However, in an edge region K of the insert molded body 1 as illustrated in FIG. 4, the metal thin-film layer 112 of the metallic decorative sheet 110 may have a contact with the thermoplastic resin molded body 120. However, it is difficult for the metal thin-film layer 112 to have a close contact with the thermoplastic resin molded body 120; in addition, if adhered by an alkaline solution such as a bleaching agent or the like, it is easy for the metal thin-film layer 112 to be dissolved (corroded) by the alkaline solution. Thereby, the metallic decorative sheet 110 would detach from the thermoplastic resin molded body 120 in the edge region K, which deteriorates the visual appearance of the product.